The present invention relates generally to the combustion of fuel oil, and more particularly to the atomization of fuel oil in a combustion furnace. In particular, the present invention provides apparatus and methods for discharging atomized fuel which provide low levels of air pollution emissions, such as oxides of nitrogen (NOx), carbon monoxide (CO), particulate matter (PM) and opacity while operating at low excess oxygen levels for improved efficiency.
For environmental and economical reasons, there is an ongoing need to improve the efficiency of fuel oil atomizers which supply fuel oil to a furnace. In particular, it is well known that xe2x80x9cheavyxe2x80x9d fuel oil (e.g., heavy number 6 oil or xe2x80x9cbunkerxe2x80x9d oil), which contains organically bound nitrogen and sulfur compounds and has a high asphaltene content, is difficult to combust while producing low air polluting emissions. Particulate matter (PM) in the form of ash and unburned carbon, carbon monoxide (CO) or partially oxidized carbon, oxides of nitrogen (NOx), and opacity are in particular troublesome air emissions for many furnaces burning heavy oil. It is known that the formation of NOx can be reduced by providing fuel-rich and fuel-lean zones in the atomizing spray pattern.
It would be advantageous to provide apparatus and methods for atomizing fuel oil which reduce NOx emissions, while also improving or maintaining CO, PM and opacity generation. It would be particularly advantageous to provide for the discharge of atomized fuel oil into a combustion chamber with effective fuel spray droplet breakup and both circumferential and radial fuel to air ratio staging in order to lower peak flame temperature and reduce NOx emissions. It would be even further advantageous to provide for the atomized fuel oil droplets discharged into the combustion chamber to be of such a sufficiently small diameter to enable rapid fuel evaporation and complete combustion for low CO emission and thorough carbon burnout with low excess oxygen levels. The methods and apparatus of the present invention provide the above-mentioned and other advantages
The present invention relates to a fuel oil atomizer and methods for discharging atomized fuel oil, e.g., into a combustion chamber of a furnace. In particular, the present invention relates to a two phase fuel oil atomizer which utilizes a secondary media such as high pressure steam or air to assist in the atomization of fuel oil, such as heavy fuel oil, while reducing NOx and other polluting emissions.
In an exemplary embodiment of the invention, a fuel oil atomizer comprises a mixing plate and a sprayer plate. The mixing plate may have a plurality of distributor openings for receiving a first material (e.g., fuel) and a plurality of central openings for receiving a second material (e.g., an atomizing media). It should be appreciated that the distributor openings can be adapted to receive either fuel or the atomizing media, with the central openings adapted to receive the other of either fuel or the atomizing media. The atomizing media may be high pressure steam or air, or any other suitable atomizing media.
The sprayer plate is adapted to engage the mixing plate in order to force the first material to mix with the second material. The sprayer plate may have an enclosed mixing chamber formed by the mixing plate and a cavity of the sprayer plate for mixing the first material traveling through the mixing plate with the second material traveling through the mixing plate. A plurality of sprayer plate openings may extend through a semi-spherical outer wall of the sprayer plate to enable atomized fuel to be expelled from the mixing chamber. The plurality of sprayer plate openings may be arranged on at least one annulus of the outer wall of the sprayer plate for expelling the atomized fuel at an at least one spray angle.
There may be at least two sets of sprayer plate openings provided. Each set of sprayer plate openings may have respective dimensions and may be arranged on respective annuli of the outer wall of the sprayer plate for expelling atomized fuel at respective spray angles. The respective dimensions of each set of openings may be successively smaller dimensions. The respective annuli may be successively smaller annuli. The respective spray angles may be successively smaller spray angles.
In an alternate embodiment, the plurality of sprayer plate openings may comprise four sets of openings. A first set of openings may have a first dimension and may be arranged on an first annulus of the outer wall of the sprayer plate for expelling atomized fuel at a first spray angle. A second set of openings may have a second dimension and may be arranged on a second annulus of the outer wall of the sprayer plate for expelling atomized fuel at a second spray angle. A third set of openings may have a third dimension and may be arranged on a third annulus of the outer wall of the sprayer plate for expelling atomized fuel at a third spray angle. A fourth set of openings may have a fourth dimension and may be arranged on a fourth annulus of the outer wall of the sprayer plate for expelling atomized fuel at a fourth spray angle.
The first dimension, second dimension, third dimension and fourth dimension may be successively smaller dimensions. The first annulus, second annulus, third annulus, and fourth annulus may be arranged on successively smaller annuli of the outer wall. The first spray angle, second spray angle, third spray angle, and fourth spray angle may be successively smaller spray angles.
In a further embodiment, the first set of openings may comprise two series of equally spaced openings, one series of openings arranged at a top portion of the first annulus and the other series of openings arranged at a bottom portion of the first annulus. The second set of openings may comprise two series of equally spaced openings, one series of openings arranged at a top portion of the second annulus and the other series of openings arranged at a bottom portion of the second annulus. The third set of openings may comprise two series of equally spaced openings, one series of openings arranged at a top portion of the third annulus and the other series of openings arranged at a bottom portion of the third annulus. The fourth set of openings may comprise two series of equally spaced openings, one series of openings arranged at a top portion of the fourth annulus and the other series of openings arranged at a bottom portion of the fourth annulus.
The first spray angle of the first set of openings may be in the range of approximately 80 to 90 degrees. The second spray angle of the second set of openings may be approximately 60 degrees. The third spray angle of the third set of openings may be approximately 40 degrees. The fourth spray angle of the fourth set of openings may be approximately 20 degrees.
Each series of openings of the first set of openings may have a first total angular separation. Each series of openings of the second set of openings may have a second total angular separation. Each series of openings of the third set of openings may have a third total angular separation. The first total angular separation may be approximately 105 degrees. The second total angular separation may be approximately 26 degrees. The third total angular separation may be approximately 36 degrees. Each series of openings of the fourth set of openings may comprise a single opening.
The first set of openings may comprise approximately 66% of total hole flow area of the sprayer plate. The second set of openings may comprise approximately 20% of the total hole flow area of the sprayer plate. The third set of openings may comprise approximately 10% of the total hole flow area of the sprayer plate. The fourth set of openings may comprise approximately 4% of the total hole flow area of the sprayer plate.
The mixing chamber may preferably have a chamber length to chamber diameter ratio in the range of about 0.75:1 to 1.25:1.
The mixing plate may further comprise a plurality of metering slots arranged on an inner portion of the mixing plate and coupling the distributor openings with the central openings.
As discussed above, the first material may be fuel oil and the second material may be an atomizing media, such as steam or air. In such a configuration, the total geometric area ratio of all central openings to all metering slots is preferably in a range from about 0.6:1 to 0.8:1. In the alternative, the first material may be an atomizing media and the second material may be fuel oil. In such a configuration, the total geometric area ratio of all central openings to all metering slots is preferably in a range of about 1.2:1 to 1.7:1.
The total area ratio of all distributor openings to all metering slots is preferably at least 1.7:1. However, the total area ratio of all distributor openings to all metering slots should be at least 1.7:1 and not greater than approximately 3:1.
In an alternate embodiment, the plurality of distributor openings may be arranged on an outer annulus of the mixing plate and may extend through the mixing plate. The plurality of central openings may be arranged on an inner annulus of the mixing plate and may extend through the mixing plate. The plurality of metering slots couple the outer annulus with the inner annulus.
In a preferred embodiment, the fuel oil atomizer comprises a mixing plate and a sprayer plate. The mixing plate may have an outer portion and an inner portion. A plurality of distributor openings may be arranged on an outer annulus of the mixing plate and may extend through the mixing plate. A plurality of central openings may be arranged on an inner annulus of the mixing plate and may extend through the mixing plate. A plurality of metering slots may be arranged on the inner portion of the mixing plate and couple the outer annulus with the inner annulus. The sprayer plate in the preferred embodiment may have a first wall for engaging a portion of the inner portion of the mixing plate such that a first material traveling through the distributor openings is forced into the metering slots for mixture with a second material traveling through the central openings. The sprayer plate may also have a semi-spherical outer wall extending from the first wall and forming a cavity. A plurality of sprayer plate openings extending through the outer wall of the sprayer plate may also be provided to enable atomized fuel to be expelled from the sprayer plate openings. The plurality of sprayer plate openings may comprise four sets of openings.
A first set of openings may have a first dimension and may be arranged on an first annulus of the outer wall of the sprayer plate for expelling atomized fuel at a first spray angle. A second set of openings may have a second dimension and may be arranged on a second annulus of the outer wall of the sprayer plate for expelling atomized fuel at a second spray angle. A third set of openings may have a third dimension and may be arranged on a third annulus of the outer wall of the sprayer plate for expelling atomized fuel at a third spray angle. A fourth set of openings may have a fourth dimension and may be arranged on a fourth annulus of the outer wall of the sprayer plate for expelling atomized fuel at a fourth spray angle.
In the preferred embodiment, an enclosed mixing chamber is formed by the mixing plate and the sprayer plate cavity for mixing the first material traveling through the distributor openings with the second material traveling through the central openings.
In addition, the first dimension, second dimension, third dimension and fourth dimension may be successively smaller dimensions. The first annulus, second annulus, third annulus, and fourth annulus may be arranged on successively smaller annuli of the sprayer plate outer wall. The first spray angle, second spray angle, third spray angle, and fourth spray angle may be successively smaller spray angles.
The four sets of openings provided in the preferred embodiment may each comprise two series of openings. The first set of openings may comprise two series of equally spaced openings, one series of openings arranged at a top portion of the first annulus and the other series of openings arranged at a bottom portion of the first annulus. The second set of openings may comprise two series of equally spaced openings, one series of openings arranged at a top portion of the second annulus and the other series of openings arranged at a bottom portion of the second annulus. The third set of openings may comprise two series of equally spaced openings, one series of openings arranged at a top portion of the third annulus and the other series of openings arranged at a bottom portion of the third annulus. The fourth set of openings may comprise two series of equally spaced openings, one series of openings arranged at a top portion of the fourth annulus and the other series of openings arranged at a bottom portion of the fourth annulus.
Each series of openings of the first set of openings may have a first total angular separation. Each series of openings of the second set of openings may have a second total angular separation. Each series of openings of the third set of openings may have a third total angular separation. Each series of openings of the fourth set of openings may have a fourth total angular separation.
A sprayer plate for use with a mixing plate to atomize fuel oil is provided having a first wall adapted to engage the mixing plate to force a first material to mix with a second material. A cavity of the sprayer plate forms an enclosed mixing chamber when the first wall is engaged with the mixing plate for mixing the first material with the second material. A plurality of sprayer plate openings extend through a semi-spherical outer wall of the sprayer plate to enable atomized fuel to be expelled from the mixing chamber. The plurality of sprayer plate openings may be arranged on at least one annulus of the outer wall of the sprayer plate for expelling the atomized fuel at an at least one spray angle.
For example, at least two sets of the sprayer plate openings may be provided, each set having respective dimensions and being arranged on respective annuli of the outer wall of the sprayer plate for expelling atomized fuel at respective spray angles. The respective dimensions of each set of openings may be successively smaller dimensions. The respective annuli may be successively smaller annuli. The respective spray angles may be successively smaller spray angles.
The plurality of sprayer plate openings may comprise four sets of openings. A first set of openings may have a first dimension and may be arranged on a first annulus of the outer wall of the sprayer plate for expelling atomized fuel at a first spray angle. A second set of openings may have a second dimension and may be arranged on a second annulus of the outer wall of the sprayer plate for expelling atomized fuel at a second spray angle. A third set of openings may have a third dimension and may be arranged on a third annulus of the outer wall of the sprayer plate for expelling atomized fuel at a third spray angle. A fourth set of openings may have a fourth dimension and may be arranged on a fourth annulus of the outer wall of the sprayer plate for expelling atomized fuel at a fourth spray angle.
The first dimension, second dimension, third dimension and fourth dimension may be successively smaller dimensions. The first annulus, second annulus, third annulus, and fourth annulus may be arranged on successively smaller annuli of the outer wall. The first spray angle, second spray angle, third spray angle, and fourth spray angle may be successively smaller spray angles.
The first set of sprayer plate openings may comprise two series of equally spaced openings, one series of openings arranged at a top portion of the first annulus and the other series of openings arranged at a bottom portion of the first annulus. The second set of openings may comprise two series of equally spaced openings, one series of openings arranged at a top portion of the second annulus and the other series of openings arranged at a bottom portion of the second annulus. The third set of openings may comprise two series of equally spaced openings, one series of openings arranged at a top portion of the third annulus and the other series of openings arranged at a bottom portion of the third annulus. The fourth set of openings may comprise two series of equally spaced openings, one series of openings arranged at a top portion of the fourth annulus and the other series of openings arranged at a bottom portion of the fourth annulus.
The first spray angle of the first set of openings may be in the range of approximately 80 to 90 degrees. The second spray angle of the second set of openings may be approximately 60 degrees. The third spray angle of the third set of openings may be approximately 40 degrees. The fourth spray angle of the fourth set of openings may be approximately 20 degrees.
Each series of openings of the first set of openings may have a first total angular separation. Each series of openings of the second set of openings may have a second total angular separation. Each series of openings of the third set of openings may have a third total angular separation. The first total angular separation may be approximately 105 degrees. The second total angular separation may be approximately 26 degrees. The third total angular separation may be approximately 36 degrees. Each series of openings of the fourth set of openings may comprise a single opening.
The first set of openings may comprise approximately 66% of total hole flow area of the sprayer plate. The second set of openings may comprise approximately 20% of the total hole flow area of the sprayer plate. The third set of openings may comprise approximately 10% of the total hole flow area of the sprayer plate. The fourth set of openings may comprise approximately 4% of the total hole flow area of the sprayer plate.
The mixing chamber may have a chamber length to chamber diameter ratio in the range of about 0.75:1 to 1.25:1.
A mixing plate for use with a sprayer plate for atomizing fuel oil is provided. A plurality of distributor openings may be arranged on an outer annulus of the mixing plate and may extend through the mixing plate. A plurality of central openings may be arranged on an inner annulus of the mixing plate and may extend through the mixing plate. A plurality of metering slots may be arranged on an inner portion of the mixing plate and may couple the outer annulus with the inner annulus. The inner portion of the mixing plate is adapted to engage the sprayer plate such that a first material traveling through the distributor openings is forced through the metering slots to mix with a second material traveling through the central openings.
The total area ratio of all distributor openings to all metering slots is preferably at least 1.7:1. However, the total area ratio of all distributor openings to all metering slots may be at least 1.7:1 and not greater than 3:1.
The metering slots may be formed by wedge shaped portions of the inner portion of the mixing plate. The wedge shaped portions may have a larger dimension at the outer annulus than at the inner annulus.
The first material (traveling through the distributor openings and the metering slots) may be fuel. The second material traveling through the central openings may be an atomizing media. In such a configuration, the total geometric area ratio of all central openings to all metering slots may be in a range from about 0.6:1 to 0.8:1.
Where the first material is an atomizing media and the second material is fuel, the total geometric area ratio of all central openings to all metering slots may be in a range of about 1.2:1 to 1.7:1.
A method for discharging atomized fuel oil is also provided. Fuel oil is mixed with an atomizing media in a mixing chamber to produce atomized fuel. The atomized fuel is expelled from the mixing chamber through a plurality of sprayer plate openings. These sprayer plate openings extend through a semi-spherical outer wall of the mixing chamber, and may be arranged on at least one annulus of the outer wall of the mixing chamber for expelling the atomized fuel at an at least one spray angle.
The atomized fuel may be expelled from the plurality of sprayer plate openings at a variety of spray angles. The atomized fuel may be expelled in a spray pattern having distinct rich and lean fuel zones.
The atomized fuel may be expelled from at least two sets of the sprayer plate openings, each set having respective dimensions and being arranged on respective annuli of the outer wall of the mixing chamber.
The plurality of sprayer plate openings may comprise four sets of openings. A first set of openings may have a first dimension and may be arranged on an first annulus of the outer wall of the sprayer plate for expelling atomized fuel at a first spray angle. A second set of openings may have a second dimension and may be arranged on a second annulus of the outer wall of the sprayer plate for expelling atomized fuel at a second spray angle. A third set of openings may have a third dimension and may be arranged on a third annulus of the outer wall of the sprayer plate for expelling atomized fuel at a third spray angle. A fourth set of openings may have a fourth dimension and may be arranged on a fourth annulus of the outer wall of the sprayer plate for expelling atomized fuel at a fourth spray angle.
The first dimension, second dimension, third dimension and fourth dimension may be successively smaller dimensions. The first annulus, second annulus, third annulus, and fourth annulus may be arranged on successively smaller annuli of the outer wall. The first spray angle, second spray angle, third spray angle, and fourth spray angle may be successively smaller spray angles.
The first set of openings may comprise two series of equally spaced openings, one series of openings arranged at a top portion of the first annulus and the other series of openings arranged at a bottom portion of the first annulus. The second set of openings may comprise two series of equally spaced openings, one series of openings arranged at a top portion of the second annulus and the other series of openings arranged at a bottom portion of the second annulus. The third set of openings may comprise two series of equally spaced openings, one series of openings arranged at a top portion of the third annulus and the other series of openings arranged at a bottom portion of the third annulus. The fourth set of openings may comprise two series of equally spaced openings, one series of openings arranged at a top portion of the fourth annulus and the other series of openings arranged at a bottom portion of the fourth annulus.
The first spray angle of the first set of openings may be in the range of approximately 80 to 90 degrees. The second spray angle of the second set of openings may be approximately 60 degrees. The third spray angle of the set plurality of openings may be approximately 40 degrees. The fourth spray angle of the fourth plurality of openings may be approximately 20 degrees.
Each series of openings of the first set of openings may have a first total angular separation. Each series of openings of the second set of openings may have a second total angular separation. Each series of openings of the third set of openings may have a third total angular separation.
The first total angular separation may be approximately 105 degrees. The second total angular separation may be approximately 26 degrees. The third total angular separation may be approximately 36 degrees. Each series of openings of the fourth set of openings may comprise a single opening.
The first set of openings may comprise approximately 66% of total hole flow area of the sprayer plate. The second set of openings may comprise approximately 20% of the total hole flow area of the sprayer plate. The third set of openings may comprise approximately 10% of the total hole flow area of the sprayer plate. The fourth set of openings may comprise approximately 4% of the total hole flow area of the sprayer plate.